Tripyramids and associated defects in epitaxial silicon layers

Abstract

Tripyramids and the associated defects present in epitaxial Si layers grown on (111) Si substrates have been examined by transmission electron microscopy and selected-area transmission electron diffraction, and their nature and crystallography directly determined. The tripyramids consist of a central triangular area, twinned about the (111) substrate plane, together with three surrounding segments, each initially twinned about the (111) substrate plane and subsequently twinned about an inclined {111} plane. The associated defects mostly consist of micro-twin lamellae, each twinned about an inclined {111} plane. The different types of interface occurring in the tripyramids are discussed, and mechanisms are suggested to account for the formation of both the tripyramids and the associated defects.